1. Field of the Invention
The invention relates to bow and/or stern thrusters on water craft. More particularly, the invention relates to bow/stern thruster control apparatus. More particularly yet, the invention relates to such apparatus for small water craft.
2. Description of the Prior Art
Thruster propulsion systems for water craft are well-known, although most such systems are designed for large vessels. Thrusters operate by drawing water through a channel and expelling it in a particular direction. The force of the expulsion of the water creates a reactive force that moves the boat in a direction opposite to the direction of the water expulsion. The use of bow and/or stern thrusters improves the maneuverability of a boat by allowing the boat to move in a direction lateral to the normal travel direction of the boat, thereby making it easier to turn the boat or to position it alongside a dock. This increased maneuverability makes it much easier, for example, to maneuver boats in crowded marinas or to bring a boat sideways up to a dock to tie up or load/unload goods. Typically, if a boat is equipped with a bow thruster and a stern thruster, the thrusters can be operated singularly or simultaneously. One such conventional thruster is disclosed in U.S. Pat. No. 6,009,822 (Aron; issued Jan. 4, 2000). In place of, or in addition to a bow and/or stern thruster, some water craft have a fore-and-aft thruster, which provides greater control over thrust in the fore-and-aft direction than does the main propulsion engine.
The action of the thruster is generally controlled by a stick on a control panel located at the helm of the boat. The stick is typically a joystick or swivel stick that has movement about a single axis or a double axis. The position of the stick controls the opening and closing of a valve, which, in turn, controls the amount of thrust generated by the thruster. The Hinckley Boat Co., for example, uses a double-axis swivel-stick as a control stick for a bow thruster. As with conventional thruster joysticks, this swivel-stick is spring-loaded, so that it returns to a helm neutral position when the operator lets go of it. This is often a disadvantage, particularly with small water craft in which there is often only one person to operate the boat and to secure it alongside a dock. When the operator lets go of the stick to secure the boat, the stick snaps back to the helm neutral position, and the boat veers away from the desired position. As a result, the automatic return of the control stick to the neutral position makes it difficult, for example, for the operator to tie up alongside the dock or to turn to some other task that requires the boat to stay in a particular position, such as alongside the dock.
One way of solving this problem is to construct a joystick that does not return to the neutral position. For example, it is conceivable to construct a thruster control in which preset valve positions, such as xc2xc open, xc2xd open, or wide open, can be selected. The disadvantage of this solution is that it would require a number of metering valves and thus would result in a system that is very expensive.
What is needed, therefore, is inexpensive thruster control apparatus that will allow a boat operator to operate a bow and/or stern thruster on a boat to maneuver the boat, including moving it sideways or rotating it about its longitudinal axis, and bring to it into position alongside a dock. What is further needed is such apparatus that would allow the operator to lock the operation of the thrusters into position in order to maintain the position of the boat alongside a dock, without having to maintain physical control of the thruster control. What is yet further needed is such apparatus that would include a fore-and-aft thruster and could be used as a come-home engine in case of main propulsion engine failure.
For the above-cited reasons, it is an object of the present invention to provide an inexpensive thruster control apparatus that will enable the operator of a boat to maneuver the boat into position along side a dock. It is a further object of the invention to provide such apparatus that will allow the thruster controls to be locked into position so as to maintain a docking position of the boat while the operator physically releases the thruster controls. It is a yet further object to provide such apparatus that has a fore-and-aft thruster and further, that can be used as a comehome engine.
The objects are achieved by providing thruster control apparatus that provides a control stick and a xe2x80x9cHOLDxe2x80x9d switch for controlling each thruster. The thrusters used are conventional thrusters, such as a motor mounted above a shifter that runs a 90xc2x0 gear box. In the Preferred Embodiment, the thrusters are operated by a hydraulic pump system, although other operating systems such as an electrically-operated or pneumatically-operated systems are also possible.
In a first embodiment of the invention, the apparatus provides a thruster control panel in the helm of the boat. The control panel has two single-axis control joysticks, a HOLD button associated with each joystick, an ON button, and an OFF button. The ON/OFF buttons are push-on/push-off buttons that are used to turn the pump operating system on and off. The joysticks and buttons are electrically connected with a central processing unit (CPU) that is powered by 24 V DC. The CPU electrically actuates a hydraulic valve that controls the amount of thrust from the stem thruster and/or a hydraulic valve that controls the amount of thrust from the bow thruster. The amount of thrust is initially proportional to the position of the respective thruster joystick. The bow and stem thrusters are conventional athwart-ship-thrusters, such as thrusters that are arranged athwart-ship in a tunnel that extends through the stem or stern, or retractable LEWMAR thrusters that drop down into the water.
The operating system is switched on when the ON button is actuated. The amount offlow of fluid pumped by the operating system through a thruster valve determines the amount of thrust generated by the respective thruster. In normal operation, the thruster valve opens or closes proportionally to a displacement of the control stick that is associated with that particular thruster valve. When the associated HOLD button is actuated, however, the apparatus according to the invention sends an electrical signal to the CPU to ignore any change in position of the joystick and to maintain the same amount of flow of operating fluid through the valve, i.e., to maintain the same amount of thrust generated by the thrusters. Accordingly, once the HOLD button is actuated, the joystick may snap back to a neutral position after the operator releases it without influencing the open position of the thruster valve. Instead, the valve holds the same open state it had when the HOLD button was set to the ON position. In this way, the same amount of thrust is maintained through the respective thruster that was being provided when the HOLD button was set to the ON position.
In the Preferred Embodiment, the apparatus provides control of a third thruster, in addition to the stern and bow thrusters of the first embodiment. In this Preferred Embodiment, the joystick that controls the stern thruster is a double-axis joystick that is also connected with a third thruster, a fore-and-aft thruster. The fore-and-aft thruster provides a thrust that propels the boat in the fore or aft direction. When the double-axis stick is moved in the port or starboard direction, the stern thruster is controlled; when moved in the fore or aft direction, the fore-and-aft thruster is controlled. Accordingly, two HOLD buttons are provided for this joystickxe2x80x94one for each of the two thrusters controlled by the stick. In an alternative embodiment, single-axis control sticks and two HOLD buttons are provided to control respectively the second and third thrusters.
In all embodiments, the thrusters can be connected to the on-board generator and be used as a xe2x80x9ccome-homexe2x80x9d engine in the case of failure of the main propulsion engine.